Field of the Disclosure
Exemplary embodiments of the present disclosure relate to a gas turbine.
Description of the Related Art
Generally, a turbine is a machine which converts energy of fluid such as water, gas, or steam into mechanical work. Typically, a turbo machine, in which a plurality of blades are embedded around a circumferential portion of a rotating body so that the rotating body is rotated at a high speed by impulsive force or reactive force generated by discharging steam or gas to the blades, is referred to as a turbine.
Such turbines are classified into a water turbine using energy of elevated water, a steam turbine using energy of steam, an air turbine using energy of high-pressure compressed air, a gas turbine using energy of high-temperature/high-pressure gas, and so forth.
The gas turbine includes a compressor, a combustor, a turbine, and a rotor.
The compressor includes a plurality of compressor vanes and a plurality of compressor blades which are alternately arranged.
The combustor is configured to supply fuel to air compressed by the compressor and ignite the fuel mixture using a burner, thus generating high-temperature and high-pressure combustion gas.
The turbine includes a plurality of turbine vanes and a plurality of turbine blades which are alternately arranged.
The rotor is provided passing through central portions of the compressor, the combustor, and the turbine. Opposite ends of the rotor are rotatably supported by bearings. One end of the rotor is coupled to a driving shaft of a generator.
The rotor includes a plurality of compressor rotor disks coupled to the respective compressor blades, a plurality of turbine rotor disks coupled to the respective turbine blades, and a torque tube configured to transmit rotating force from the turbine rotor disks to the compressor rotor disks.
In the gas turbine having the above-mentioned configuration, air compressed by the compressor is mixed with fuel and combusted in the combustor, and then is converted into high-temperature combustion gas. The combustion gas formed in the foregoing manner is discharged toward the turbine. The discharged combustion gas passes through the turbine blades and thus generates rotating force. Thereby, the rotor is rotated.
The gas turbine does not have a reciprocating component such as a piston of a four-stroke engine. Therefore, mutual friction parts such as a piston-and-cylinder are not present, so that there are advantages in that there is little consumption of lubricant, the amplitude of vibration is markedly reduced unlike a reciprocating machine having high-amplitude characteristics, and high-speed driving is possible.
Unlike the compressor, the turbine comes into contact with high-temperature and high-pressure combustion gas, and therefore requires a cooling unit for preventing damage, e.g., thermal deterioration. To this end, the turbine further includes a cooling passage through which compressed air, as a cooling fluid, drawn out from portions of the compressor is supplied to the turbine. The cooling passage communicates with a turbine vane cooling passage formed in each turbine vane. The turbine vane cooling passage is provided with an impingement plate having a plurality of injection holes through which air is injected onto an inner wall of the turbine vane, so as to enhance the cooling performance.
However, in the conventional gas turbine having the above-mentioned configuration, the turbine vane is not appropriately cooled, so a temperature gradient occurs in the turbine vane, whereby the turbine vane may be damaged due to thermal stress.
Referring to U.S. Patent 2014/0219788 A1, in a turbine vane of a conventional gas turbine, air (cooling fluid) injected from injection holes of an impingement plate into an impingement space defined between the impingement plate and an inner wall of the turbine vane is impinged against the inner wall of the turbine vane and then discharged out of the turbine vane through an exit hole formed, for example, in a trailing edge of the turbine vane. Here, the injection holes include an upstream-side injection hole disposed at an upstream side with respect to a flow direction of the air in the impingement space, and a downstream-side injection hole disposed at a downstream side with respect to the flow direction of the air in the impingement space. Air that is ejected from the upstream-side injection hole and then flows toward the exit hole may impede ejection of air from the downstream-side injection hole. In other words, a so-called cross flow effect is caused. Hence, the flow rate of air ejected from the downstream-side injection hole is reduced, whereby a region facing the downstream-side injection hole may be insufficiently cooled.
Furthermore, in the conventional gas turbine, the turbine vane is formed such that the flow rate of air injected onto a region having a comparatively thin wall, such as an airfoil, is on the same level as the flow rate of air injected onto a region having a comparatively thick wall, such as a filet. Therefore, the region having the comparatively thick wall may be insufficiently cooled.